Progress in 1984 to 1985 includes carcinoma (CA)-associated Tn antigen in addition to T. We found Tn to be the immediate precursor of T. Both are universal human CA markers and autoantigens. In the former role, they are powerful in pathohistological diagnosis and frequently prognosis, while cellular and humoral anti-T autoimmune responses permit early CA detection with high sensitivity and specificity. Conformational factors are important for humoral anti-T responses. In an in vitro model, we showed T-\and Tn-specific clusters to be strongly involved in CA adhesion to hearthy tissue, one of the primary steps of CA invasion. Using desialylated human O red blood cells (T RBC) we prepared rat hybridomas producing monoclonal anti-T, and in addition those producing monoclonal anti-Tn antibodies reacting with terminal N-acetyl-d-galactosaminoyl-alpha-O-(GalNAc-alpha-O-) structures. Subsequently we showed that fully, specifically desialylated O RBC, and T antigen isolated therefrom, possess GalNAc-alpha-O-\groupings expressing Tn specificity as determined with ordinary human polychlonal anti-Tn antibodies. This finding would appear to necessitate revision of the general view that the rare naturally occurring Tn is the result of a "selective deficiency of 3-beta-d-galactosyltransferase." Rather, the somatic mutation leading to Tn is likely to have a pleiotropic effect involving both sialyl-\and galactosyltransferases. T RBC-derived T antigen (an artifact) thus resembles natural cell surface structures of well-differentiated CAs, which we recently showed to have more T than Tn; the reverse was generally true for anaplastic CAs. Four of 14 monoclonal anti-human CA antibodies given by others turned out to be anti-Tn; this indicates Tn's import in CA. Contrary to general belief, we detected immunoreactive T and Tn epitopes in human embryos (6 to 12-week-old, pretolerant stage). Biochemical studies on healthy human RBC, on guinea pig L-10 hepatoCA, and on a human breast CA culture (4 x 10[unreadable]11[unreadable] cells have now been grown) resulted in glycopeptide (GP) and glycolipid (GL) fractions with T, Tn, N, and M activity. From the RBCs we obtained homogeneous active NH[unreadable]2[unreadable]-terminal penta-, hexa-, and hepta-GPs (approximately 2 kDa) with T-specific clusters and larger, T and Tn active GPs (approximately 12 kDa). From the L-10 CA cells, we obtained T and Tn active neutral glycolipids larger than tetrahexaosyl ceramide and N and M active gangliosides; treatment with A. ureafaciens sialidase destroyed greater than 75% of their N and M activities and gave rise to a resorcinol negative component, chromatographically similar to asialo-G[unreadable]M1[unreadable], with T activity. We identified T-\and Tn-specific glycoproteins in membrane and cytoplasmic fractions of cultured human breast CA cells and partially purified these antigens by DEAE-cellulose fractionation and gel filtration on Sephacryl S-200. T active material has Gal and GalNAc (molar ratio approximately 1.5:1). The Tn active GP fraction is rich in terminal GalNAc, and Ser and Thr are prominent in both. (AG)